<PRE><B>Question 163159</B>
Call the quantity of soybean S and cornmeal C.
Write the total weight equation.
1.{{{S+C=280}}} 
Write the concentration equation.
2.{{{S*0.14+C*0.07=(S+C)*0.13}}}
2.{{{14S+7C=13(280)}}}
2.{{{14S+7C=3640}}}
Use eq. 1 to solve for S in terms of C and substitute into eq. 2,
1.{{{S+C=280}}} 
{{{S=280-C}}} 
.
.
.
2.{{{14S+7C=3640}}}
{{{14(280-C)+7C=3640}}}
{{{3920-14C+7C=3640}}}
{{{-7C=-280}}}
{{{C=40}}}
From eq. 1,
{{{S=280-C}}}
{{{S=280-40}}}
{{{S=240}}}
.
.
.
240 pounds of soybeans and 40 pounds of cornmeal. </PRE>